OPENSSL INSTALLATION
--------------------
This document describes installation on all supported operating
systems (the Linux/Unix family, OpenVMS and Windows)
To install OpenSSL, you will need:
* A make implementation
* Perl 5 with core modules (please read NOTES.PERL)
* The perl module Text::Template (please read NOTES.PERL)
* an ANSI C compiler
* a development environment in the form of development libraries and C
header files
* a supported operating system
For additional platform specific requirements, solutions to specific
issues and other details, please read one of these:
* NOTES.VMS (OpenVMS)
* NOTES.WIN (any supported Windows)
* NOTES.DJGPP (DOS platform with DJGPP)
Notational conventions in this document
---------------------------------------
Throughout this document, we use the following conventions in command
examples:
$ command Any line starting with a dollar sign
($) is a command line.
{ word1 | word2 | word3 } This denotes a mandatory choice, to be
replaced with one of the given words.
A simple example would be this:
$ echo { FOO | BAR | COOKIE }
which is to be understood as one of
these:
$ echo FOO
- or -
$ echo BAR
- or -
$ echo COOKIE
[ word1 | word2 | word3 ] Similar to { word1 | word2 | word3 }
except it's optional to give any of
those. In addition to the examples
above, this would also be valid:
$ echo
{{ target }} This denotes a mandatory word or
sequence of words of some sort. A
simple example would be this:
$ type {{ filename }}
which is to be understood to use the
command 'type' on some file name
determined by the user.
[[ options ]] Similar to {{ target }}, but is
optional.
Note that the notation assumes spaces around {, }, [, ], {{, }} and
[[, ]]. This is to differentiate from OpenVMS directory
specifications, which also use [ and ], but without spaces.
Quick Start
-----------
If you want to just get on with it, do:
on Unix:
$ ./config
$ make
$ make test
$ make install
on OpenVMS:
$ @config
$ mms
$ mms test
$ mms install
on Windows (only pick one of the targets for configuration):
$ perl Configure { VC-WIN32 | VC-WIN64A | VC-WIN64I | VC-CE }
$ nmake
$ nmake test
$ nmake install
If any of these steps fails, see section Installation in Detail below.
This will build and install OpenSSL in the default location, which is:
Unix: normal installation directories under /usr/local
OpenVMS: SYS$COMMON:[OPENSSL-'version'...], where 'version' is the
OpenSSL version number with underscores instead of periods.
Windows: C:\Program Files\OpenSSL or C:\Program Files (x86)\OpenSSL
If you want to install it anywhere else, run config like this:
On Unix:
$ ./config --prefix=/opt/openssl --openssldir=/usr/local/ssl
On OpenVMS:
$ @config --prefix=PROGRAM:[INSTALLS] --openssldir=SYS$MANAGER:[OPENSSL]
Configuration Options
---------------------
There are several options to ./config (or ./Configure) to customize
the build (note that for Windows, the defaults for --prefix and
--openssldir depend in what configuration is used and what Windows
implementation OpenSSL is built on. More notes on this in NOTES.WIN):
--api=x.y.z
Don't build with support for deprecated APIs below the
specified version number. For example "--api=1.1.0" will
remove support for all APIS that were deprecated in OpenSSL
version 1.1.0 or below.
--cross-compile-prefix=PREFIX
The PREFIX to include in front of commands for your
toolchain. It's likely to have to end with dash, e.g.
a-b-c- would invoke GNU compiler as a-b-c-gcc, etc.
Unfortunately cross-compiling is too case-specific to
put together one-size-fits-all instructions. You might
have to pass more flags or set up environment variables
to actually make it work. Android and iOS cases are
discussed in corresponding Configurations/10-main.cf
sections. But there are cases when this option alone is
sufficient. For example to build the mingw64 target on
Linux "--cross-compile-prefix=x86_64-w64-mingw32-"
works. Naturally provided that mingw packages are
installed. Today Debian and Ubuntu users have option to
install a number of prepackaged cross-compilers along
with corresponding run-time and development packages for
"alien" hardware. To give another example
"--cross-compile-prefix=mipsel-linux-gnu-" suffices
in such case. Needless to mention that you have to
invoke ./Configure, not ./config, and pass your target
name explicitly.
--debug
Build OpenSSL with debugging symbols.
--libdir=DIR
The name of the directory under the top of the installation
directory tree (see the --prefix option) where libraries will
be installed. By default this is "lib". Note that on Windows
only ".lib" files will be stored in this location. dll files
will always be installed to the "bin" directory.
--openssldir=DIR
Directory for OpenSSL configuration files, and also the
default certificate and key store. Defaults are:
Unix: /usr/local/ssl
Windows: C:\Program Files\Common Files\SSL
or C:\Program Files (x86)\Common Files\SSL
OpenVMS: SYS$COMMON:[OPENSSL-COMMON]
--prefix=DIR
The top of the installation directory tree. Defaults are:
Unix: /usr/local
Windows: C:\Program Files\OpenSSL
or C:\Program Files (x86)\OpenSSL
OpenVMS: SYS$COMMON:[OPENSSL-'version']
--release
Build OpenSSL without debugging symbols. This is the default.
--strict-warnings
This is a developer flag that switches on various compiler
options recommended for OpenSSL development. It only works
when using gcc or clang as the compiler. If you are
developing a patch for OpenSSL then it is recommended that
you use this option where possible.
--with-zlib-include=DIR
The directory for the location of the zlib include file. This
option is only necessary if enable-zlib (see below) is used
and the include file is not already on the system include
path.
--with-zlib-lib=LIB
On Unix: this is the directory containing the zlib library.
If not provided the system library path will be used.
On Windows: this is the filename of the zlib library (with or
without a path). This flag must be provided if the
zlib-dynamic option is not also used. If zlib-dynamic is used
then this flag is optional and a default value ("ZLIB1") is
used if not provided.
On VMS: this is the filename of the zlib library (with or
without a path). This flag is optional and if not provided
then "GNV$LIBZSHR", "GNV$LIBZSHR32" or "GNV$LIBZSHR64" is
used by default depending on the pointer size chosen.
no-afalgeng
Don't build the AFALG engine. This option will be forced if
on a platform that does not support AFALG.
enable-asan
Build with the Address sanitiser. This is a developer option
only. It may not work on all platforms and should never be
used in production environments. It will only work when used
with gcc or clang and should be used in conjunction with the
no-shared option.
no-asm
Do not use assembler code. On some platforms a small amount
of assembler code may still be used.
no-async
Do not build support for async operations.
no-autoalginit
Don't automatically load all supported ciphers and digests.
Typically OpenSSL will make available all of its supported
ciphers and digests. For a statically linked application this
may be undesirable if small executable size is an objective.
This only affects libcrypto. Ciphers and digests will have to
be loaded manually using EVP_add_cipher() and
EVP_add_digest() if this option is used. This option will
force a non-shared build.
no-autoerrinit
Don't automatically load all libcrypto/libssl error strings.
Typically OpenSSL will automatically load human readable
error strings. For a statically linked application this may
be undesirable if small executable size is an objective.
no-capieng
Don't build the CAPI engine. This option will be forced if
on a platform that does not support CAPI.
no-cms
Don't build support for CMS features
no-comp
Don't build support for SSL/TLS compression. If this option
is left enabled (the default), then compression will only
work if the zlib or zlib-dynamic options are also chosen.
enable-crypto-mdebug
Build support for debugging memory allocated via
OPENSSL_malloc() or OPENSSL_zalloc().
enable-crypto-mdebug-backtrace
As for crypto-mdebug, but additionally provide backtrace
information for allocated memory.
TO BE USED WITH CARE: this uses GNU C functionality, and
is therefore not usable for non-GNU config targets. If
your build complains about the use of '-rdynamic' or the
lack of header file execinfo.h, this option is not for you.
ALSO NOTE that even though execinfo.h is available on your
system (through Gnulib), the functions might just be stubs
that do nothing.
no-ct
Don't build support for Certificate Transparency.
no-deprecated
Don't build with support for any deprecated APIs. This is the
same as using "--api" and supplying the latest version
number.
no-dgram
Don't build support for datagram based BIOs. Selecting this
option will also force the disabling of DTLS.
no-dso
Don't build support for loading Dynamic Shared Objects.
no-dynamic-engine
Don't build the dynamically loaded engines. This only has an
effect in a "shared" build
no-ec
Don't build support for Elliptic Curves.
no-ec2m
Don't build support for binary Elliptic Curves
enable-ec_nistp_64_gcc_128
Enable support for optimised implementations of some commonly
used NIST elliptic curves. This is only supported on some
platforms.
enable-egd
Build support for gathering entropy from EGD (Entropy
Gathering Daemon).
no-engine
Don't build support for loading engines.
no-err
Don't compile in any error strings.
no-filenames
Don't compile in filename and line number information (e.g.
for errors and memory allocation).
enable-fuzz-libfuzzer, enable-fuzz-afl
Build with support for fuzzing using either libfuzzer or AFL.
These are developer options only. They may not work on all
platforms and should never be used in production environments.
See the file fuzz/README.md for further details.
no-gost
Don't build support for GOST based ciphersuites. Note that
if this feature is enabled then GOST ciphersuites are only
available if the GOST algorithms are also available through
loading an externally supplied engine.
enable-heartbeats
Build support for DTLS heartbeats.
no-hw-padlock
Don't build the padlock engine.
no-makedepend
Don't generate dependencies.
no-multiblock
Don't build support for writing multiple records in one
go in libssl (Note: this is a different capability to the
pipelining functionality).
no-nextprotoneg
Don't build support for the NPN TLS extension.
no-ocsp
Don't build support for OCSP.
no-pic
Don't build with support for Position Independent Code.
no-posix-io
Don't use POSIX IO capabilities.
no-psk
Don't build support for Pre-Shared Key based ciphersuites.
no-rdrand
Don't use hardware RDRAND capabilities.
no-rfc3779
Don't build support for RFC3779 ("X.509 Extensions for IP
Addresses and AS Identifiers")
sctp
Build support for SCTP
no-shared
Do not create shared libraries, only static ones. See "Note
on shared libraries" below.
no-sock
Don't build support for socket BIOs
no-srp
Don't build support for SRP or SRP based ciphersuites.
no-srtp
Don't build SRTP support
no-sse2
Exclude SSE2 code paths. Normally SSE2 extension is
detected at run-time, but the decision whether or not the
machine code will be executed is taken solely on CPU
capability vector. This means that if you happen to run OS
kernel which does not support SSE2 extension on Intel P4
processor, then your application might be exposed to
"illegal instruction" exception. There might be a way
to enable support in kernel, e.g. FreeBSD kernel can be
compiled with CPU_ENABLE_SSE, and there is a way to
disengage SSE2 code paths upon application start-up,
but if you aim for wider "audience" running such kernel,
consider no-sse2. Both the 386 and no-asm options imply
no-sse2.
enable-ssl-trace
Build with the SSL Trace capabilities (adds the "-trace"
option to s_client and s_server).
no-static-engine
Don't build the statically linked engines. This only
has an impact when not built "shared".
no-stdio
Don't use any C "stdio" features. Only libcrypto and libssl
can be built in this way. Using this option will suppress
building the command line applications. Additionally since
the OpenSSL tests also use the command line applications the
tests will also be skipped.
no-threads
Don't try to build with support for multi-threaded
applications.
threads
Build with support for multi-threaded applications. Most
platforms will enable this by default. However if on a
platform where this is not the case then this will usually
require additional system-dependent options! See "Note on
multi-threading" below.
no-ts
Don't build Time Stamping Authority support.
enable-ubsan
Build with the Undefined Behaviour sanitiser. This is a
developer option only. It may not work on all platforms and
should never be used in production environments. It will only
work when used with gcc or clang and should be used in
conjunction with the "-DPEDANTIC" option (or the
--strict-warnings option).
no-ui
Don't build with the "UI" capability (i.e. the set of
features enabling text based prompts).
enable-unit-test
Enable additional unit test APIs. This should not typically
be used in production deployments.
enable-weak-ssl-ciphers
Build support for SSL/TLS ciphers that are considered "weak"
(e.g. RC4 based ciphersuites).
zlib
Build with support for zlib compression/decompression.
zlib-dynamic
Like "zlib", but has OpenSSL load the zlib library
dynamically when needed. This is only supported on systems
where loading of shared libraries is supported.
386
On Intel hardware, use the 80386 instruction set only
(the default x86 code is more efficient, but requires at
least a 486). Note: Use compiler flags for any other CPU
specific configuration, e.g. "-m32" to build x86 code on
an x64 system.
no-
Don't build support for negotiating the specified SSL/TLS
protocol (one of ssl, ssl3, tls, tls1, tls1_1, tls1_2, dtls,
dtls1 or dtls1_2). If "no-tls" is selected then all of tls1,
tls1_1 and tls1_2 are disabled. Similarly "no-dtls" will
disable dtls1 and dtls1_2. The "no-ssl" option is synonymous
with "no-ssl3". Note this only affects version negotiation.
OpenSSL will still provide the methods for applications to
explicitly select the individual protocol versions.
no--method
As for no- but in addition do not build the methods for
applications to explicitly select individual protocol
versions.
enable-
Build with support for the specified algorithm, where
is one of: md2 or rc5.
no-
Build without support for the specified algorithm, where
is one of: bf, blake2, camellia, cast, chacha, cmac,
des, dh, dsa, ecdh, ecdsa, idea, md4, md5, mdc2, ocb,
ploy1305, rc2, rc4, rmd160, scrypt, seed or whirlpool. The
"ripemd" algorithm is deprecated and if used is synonymous
with rmd160.
-Dxxx, -lxxx, -Lxxx, -fxxx, -mXXX, -Kxxx
These system specific options will be passed through to the
compiler to allow you to define preprocessor symbols, specify
additional libraries, library directories or other compiler
options.
Installation in Detail
----------------------
1a. Configure OpenSSL for your operation system automatically:
NOTE: This is not available on Windows.
$ ./config [[ options ]] # Unix
or
$ @config [[ options ]] ! OpenVMS
For the remainder of this text, the Unix form will be used in all
examples, please use the appropriate form for your platform.
This guesses at your operating system (and compiler, if necessary) and
configures OpenSSL based on this guess. Run ./config -t to see
if it guessed correctly. If you want to use a different compiler, you
are cross-compiling for another platform, or the ./config guess was
wrong for other reasons, go to step 1b. Otherwise go to step 2.
On some systems, you can include debugging information as follows:
$ ./config -d [[ options ]]
1b. Configure OpenSSL for your operating system manually
OpenSSL knows about a range of different operating system, hardware and
compiler combinations. To see the ones it knows about, run
$ ./Configure # Unix
or
$ perl Configure # All other platforms
For the remainder of this text, the Unix form will be used in all
examples, please use the appropriate form for your platform.
Pick a suitable name from the list that matches your system. For most
operating systems there is a choice between using "cc" or "gcc". When
you have identified your system (and if necessary compiler) use this name
as the argument to Configure. For example, a "linux-elf" user would
run:
$ ./Configure linux-elf [[ options ]]
If your system isn't listed, you will have to create a configuration
file named Configurations/{{ something }}.conf and add the correct
configuration for your system. See the available configs as examples
and read Configurations/README and Configurations/README.design for
more information.
The generic configurations "cc" or "gcc" should usually work on 32 bit
Unix-like systems.
Configure creates a build file ("Makefile" on Unix, "makefile" on Windows
and "descrip.mms" on OpenVMS) from a suitable template in Configurations,
and defines various macros in include/openssl/opensslconf.h (generated from
include/openssl/opensslconf.h.in).
1c. Configure OpenSSL for building outside of the source tree.
OpenSSL can be configured to build in a build directory separate from
the directory with the source code. It's done by placing yourself in
some other directory and invoking the configuration commands from
there.
Unix example:
$ mkdir /var/tmp/openssl-build
$ cd /var/tmp/openssl-build
$ /PATH/TO/OPENSSL/SOURCE/config [[ options ]]
or
$ /PATH/TO/OPENSSL/SOURCE/Configure {{ target }} [[ options ]]
OpenVMS example:
$ set default sys$login:
$ create/dir [.tmp.openssl-build]
$ set default [.tmp.openssl-build]
$ @[PATH.TO.OPENSSL.SOURCE]config [[ options ]]
or
$ @[PATH.TO.OPENSSL.SOURCE]Configure {{ target }} [[ options ]]
Windows example:
$ C:
$ mkdir \temp-openssl
$ cd \temp-openssl
$ perl d:\PATH\TO\OPENSSL\SOURCE\Configure {{ target }} [[ options ]]
Paths can be relative just as well as absolute. Configure will
do its best to translate them to relative paths whenever possible.
2. Build OpenSSL by running:
$ make # Unix
$ mms ! (or mmk) OpenVMS
$ nmake # Windows
This will build the OpenSSL libraries (libcrypto.a and libssl.a on
Unix, corresponding on other platforms) and the OpenSSL binary
("openssl"). The libraries will be built in the top-level directory,
and the binary will be in the "apps" subdirectory.
If the build fails, look at the output. There may be reasons for
the failure that aren't problems in OpenSSL itself (like missing
standard headers). If you are having problems you can get help by
sending an email to the openssl-users email list (see
https://www.openssl.org/community/mailinglists.html for details). If it
is a bug with OpenSSL itself, please report the problem to
(note that your message will be recorded in the request
tracker publicly readable at
https://www.openssl.org/community/index.html#bugs and will be
forwarded to a public mailing list). Please check out the request
tracker. Maybe the bug was already reported or has already been
fixed.
(If you encounter assembler error messages, try the "no-asm"
configuration option as an immediate fix.)
Compiling parts of OpenSSL with gcc and others with the system
compiler will result in unresolved symbols on some systems.
3. After a successful build, the libraries should be tested. Run:
$ make test # Unix
$ mms test ! OpenVMS
$ nmake test # Windows
NOTE: you MUST run the tests from an unprivileged account (or
disable your privileges temporarily if your platform allows it).
If some tests fail, look at the output. There may be reasons for
the failure that isn't a problem in OpenSSL itself (like a
malfunction with Perl). You may want increased verbosity, that
can be accomplished like this:
$ make VERBOSE=1 test # Unix
$ mms /macro=(VERBOSE=1) test ! OpenVMS
$ nmake VERBOSE=1 test # Windows
If you want to run just one or a few specific tests, you can use
the make variable TESTS to specify them, like this:
$ make TESTS='test_rsa test_dsa' test # Unix
$ mms/macro="TESTS=test_rsa test_dsa" test ! OpenVMS
$ nmake TESTS='test_rsa test_dsa' test # Windows
And of course, you can combine (Unix example shown):
$ make VERBOSE=1 TESTS='test_rsa test_dsa' test
You can find the list of available tests like this:
$ make list-tests # Unix
$ mms list-tests ! OpenVMS
$ nmake list-tests # Windows
Have a look at the manual for the perl module Test::Harness to
see what other HARNESS_* variables there are.
If you find a problem with OpenSSL itself, try removing any
compiler optimization flags from the CFLAGS line in Makefile and
run "make clean; make" or corresponding.
Please send bug reports to .
4. If everything tests ok, install OpenSSL with
$ make install # Unix
$ mms install ! OpenVMS
$ nmake install # Windows
This will install all the software components in this directory
tree under PREFIX (the directory given with --prefix or its
default):
Unix:
bin/ Contains the openssl binary and a few other
utility scripts.
include/openssl
Contains the header files needed if you want
to build your own programs that use libcrypto
or libssl.
lib Contains the OpenSSL library files.
lib/engines Contains the OpenSSL dynamically loadable engines.
share/man/man1 Contains the OpenSSL command line man-pages.
share/man/man3 Contains the OpenSSL library calls man-pages.
share/man/man5 Contains the OpenSSL configuration format man-pages.
share/man/man7 Contains the OpenSSL other misc man-pages.
share/doc/openssl/html/man1
share/doc/openssl/html/man3
share/doc/openssl/html/man5
share/doc/openssl/html/man7
Contains the HTML rendition of the man-pages.
OpenVMS ('arch' is replaced with the architecture name, "Alpha"
or "ia64", 'sover' is replaced with the shared library version
(0101 for 1.1), and 'pz' is replaced with the pointer size
OpenSSL was built with):
[.EXE.'arch'] Contains the openssl binary.
[.EXE] Contains a few utility scripts.
[.include.openssl]
Contains the header files needed if you want
to build your own programs that use libcrypto
or libssl.
[.LIB.'arch'] Contains the OpenSSL library files.
[.ENGINES'sover''pz'.'arch']
Contains the OpenSSL dynamically loadable engines.
[.SYS$STARTUP] Contains startup, login and shutdown scripts.
These define appropriate logical names and
command symbols.
[.SYSTEST] Contains the installation verification procedure.
[.HTML] Contains the HTML rendition of the manual pages.
Additionally, install will add the following directories under
OPENSSLDIR (the directory given with --openssldir or its default)
for you convenience:
certs Initially empty, this is the default location
for certificate files.
private Initially empty, this is the default location
for private key files.
misc Various scripts.
Package builders who want to configure the library for standard
locations, but have the package installed somewhere else so that
it can easily be packaged, can use
$ make DESTDIR=/tmp/package-root install # Unix
$ mms/macro="DESTDIR=TMP:[PACKAGE-ROOT]" install ! OpenVMS
The specified destination directory will be prepended to all
installation target paths.
Compatibility issues with previous OpenSSL versions:
* COMPILING existing applications
OpenSSL 1.1.0 hides a number of structures that were previously
open. This includes all internal libssl structures and a number
of EVP types. Accessor functions have been added to allow
controlled access to the structures' data.
This means that some software needs to be rewritten to adapt to
the new ways of doing things. This often amounts to allocating
an instance of a structure explicitly where you could previously
allocate them on the stack as automatic variables, and using the
provided accessor functions where you would previously access a
structure's field directly.
Some APIs have changed as well. However, older APIs have been
preserved when possible.
Environment Variables
---------------------
A number of environment variables can be used to provide additional control
over the build process. Typically these should be defined prior to running
config or Configure. Not all environment variables are relevant to all
platforms.
AR
The name of the ar executable to use.
CC
The compiler to use. Configure will attempt to pick a default
compiler for your platform but this choice can be overridden
using this variable. Set it to the compiler executable you wish
to use, e.g. "gcc" or "clang".
CROSS_COMPILE
This environment variable has the same meaning as for the
"--cross-compile-prefix" Configure flag described above. If both
are set then the Configure flag takes precedence.
NM
The name of the nm executable to use.
OPENSSL_LOCAL_CONFIG_DIR
OpenSSL comes with a database of information about how it
should be built on different platforms as well as build file
templates for those platforms. The database is comprised of
".conf" files in the Configurations directory. The build
file templates reside there as well as ".tmpl" files. See the
file Configurations/README for further information about the
format of ".conf" files as well as information on the ".tmpl"
files.
In addition to the standard ".conf" and ".tmpl" files, it is
possible to create your own ".conf" and ".tmpl" files and store
them locally, outside the OpenSSL source tree. This environment
variable can be set to the directory where these files are held
and will have Configure to consider them in addition to the
standard ones.
PERL
The name of the Perl executable to use when building OpenSSL.
HASHBANGPERL
The command string for the Perl executable to insert in the
#! line of perl scripts that will be publically installed.
Default: /usr/bin/env perl
Note: the value of this variable is added to the same scripts
on all platforms, but it's only relevant on Unix-like platforms.
RC
The name of the rc executable to use. The default will be as
defined for the target platform in the ".conf" file. If not
defined then "windres" will be used. The WINDRES environment
variable is synonymous to this. If both are defined then RC
takes precedence.
RANLIB
The name of the ranlib executable to use.
WINDRES
See RC.
Makefile targets
----------------
The Configure script generates a Makefile in a format relevant to the specific
platform. The Makefiles provide a number of targets that can be used. Not all
targets may be available on all platforms. Only the most common targets are
described here. Examine the Makefiles themselves for the full list.
all
The default target to build all the software components.
clean
Remove all build artefacts and return the directory to a "clean"
state.
depend
Rebuild the dependencies in the Makefiles. This is a legacy
option that no longer needs to be used in OpenSSL 1.1.0.
install
Install all OpenSSL components.
install_sw
Only install the OpenSSL software components.
install_docs
Only install the OpenSSL documentation components.
install_man_docs
Only install the OpenSSL man pages (Unix only).
install_html_docs
Only install the OpenSSL html documentation.
list-tests
Prints a list of all the self test names.
test
Build and run the OpenSSL self tests.
uninstall
Uninstall all OpenSSL components.
update
This is a developer option. If you are developing a patch for
OpenSSL you may need to use this if you want to update
automatically generated files; add new error codes or add new
(or change the visibility of) public API functions. (Unix only).
Note on multi-threading
-----------------------
For some systems, the OpenSSL Configure script knows what compiler options
are needed to generate a library that is suitable for multi-threaded
applications. On these systems, support for multi-threading is enabled
by default; use the "no-threads" option to disable (this should never be
necessary).
On other systems, to enable support for multi-threading, you will have
to specify at least two options: "threads", and a system-dependent option.
(The latter is "-D_REENTRANT" on various systems.) The default in this
case, obviously, is not to include support for multi-threading (but
you can still use "no-threads" to suppress an annoying warning message
from the Configure script.)
OpenSSL provides built-in support for two threading models: pthreads (found on
most UNIX/Linux systems), and Windows threads. No other threading models are
supported. If your platform does not provide pthreads or Windows threads then
you should Configure with the "no-threads" option.
Note on shared libraries
------------------------
For most systems the OpenSSL Configure script knows what is needed to
build shared libraries for libcrypto and libssl. On these systems
the shared libraries will be created by default. This can be suppressed and
only static libraries created by using the "no-shared" option. On systems
where OpenSSL does not know how to build shared libraries the "no-shared"
option will be forced and only static libraries will be created.
Note on random number generation
--------------------------------
Availability of cryptographically secure random numbers is required for
secret key generation. OpenSSL provides several options to seed the
internal PRNG. If not properly seeded, the internal PRNG will refuse
to deliver random bytes and a "PRNG not seeded error" will occur.
On systems without /dev/urandom (or similar) device, it may be necessary
to install additional support software to obtain a random seed.
Please check out the manual pages for RAND_add(), RAND_bytes(), RAND_egd(),
and the FAQ for more information.